WASHINGTON (Reuters) – The U.S. Supreme Court on Tuesday appeared closely divided with likely pivotal vote Justice Anthony Kennedy posing tough questions about a Christian baker’s refusal to make a wedding cake for a gay couple but also questioning whether a Colorado civil rights commission that ruled on the issue was biased against religion.

The nine justices heard an intense, extended 80-minute oral argument in the major case on whether certain businesses can refuse service to gay couples if they oppose same-sex marriage on religious grounds.

The case concerns an appeal by Jack Phillips, a baker who runs Masterpiece Cakeshop in the Denver suburb of Lakewood, of a state court ruling that his refusal to make a cake for gay couple David Mullins and Charlie Craig in 2012 on the basis of his religious beliefs violated a Colorado anti-discrimination law.

Kennedy, a conservative who sometimes sides with the court’s four liberals in major cases, raised concerns about issuing a ruling siding with the baker that would give a green light to discrimination against gay people.

The court’s four liberals would likely side with him on that point, with several justices citing a wide range of other creative professionals, including makeup artists and florists, who could deny service to gay customers if the baker wins.

In one of the biggest cases of the conservative-majority court’s nine-month term, the justices must decide whether the baker’s action was constitutionally protected.

Phillips, represented by the conservative Christian advocacy group Alliance Defending Freedom, contends that the Colorado law violated his rights to freedom of speech and free exercise of religion under the U.S. Constitution’s First Amendment. The Supreme Court arguments focused on his free speech claim, based on the idea that creating a custom cake is a form of free expression.

Mullins and Craig call the baker’s refusal a simple case of unlawful discrimination based on sexual orientation. Colorado law bars businesses from refusing service based on race, sex, marital status or sexual orientation.

Kennedy, a long-term champion of gay rights, mentioned the possibility of a baker putting a sign in his window saying he would not make cakes for gay weddings, wondering if that would be “an affront to the gay community.”

But citing comments made by a commissioner on the state civil rights panel that ruled against the baker, Kennedy said there was evidence of “hostility to religion” and questioned whether that panel’s decision should be allowed to stand.

“Tolerance is essential in a free society. Tolerance is most meaningful when it’s mutual,” Kennedy said. But the commission was not “tolerant or respectful” of Phillips, he added.

The commissioner, unnamed in court papers, said at a 2014 hearing that “freedom of religion, and religion, has been used to justify all kinds of discrimination throughout history.” The commissioner added that freedom of religion “is one of the most despicable pieces of rhetoric that people can use … to use their religion to hurt others.”

It was unclear to what extent Kennedy’s criticism of the commissioner would dictate how he votes in the case.

The Supreme Court legalized gay marriage in a landmark 2015 ruling written by the 81-year-old Kennedy, one of the court’s five conservatives. He has joined the court’s four liberals in major decisions on issues such as abortion and gay rights, but also is a strong proponent of free speech rights. [L2N1LU1W9]

Mullins and Craig are represented by the American Civil Liberties Union, which has argued that Phillips’ legal team is advocating for a “license to discriminate” that could have broad repercussions beyond gay rights.

Several of the justices asked questions that suggested they are concerned about how far a ruling in favor of the baker might extend. Liberal Justice Elena Kagan wondered about whether a hairstylist, chef or a makeup artist could refuse service, claiming their services are also speech protected by the Constitution. “Why is there no speech in creating a wonderful hairdo?” Kagan asked.

Kennedy asked U.S. Solicitor General Noel Francisco, the Trump administration lawyer supporting the baker, what would happen if the court rules for the baker and then bakers nationwide then started receiving requests to not bake cakes for gay weddings. “Would the government feel vindicated?” Kennedy asked.

Conservative members of the court, including Chief Justice John Roberts, appeared more sympathetic to the baker.

‘LOVE WINS’

Hundreds of demonstrators on both sides of the dispute rallied outside the white marble courthouse. Supporters of Phillips waved signs that read, “We got your back Jack.” As Mullins and Craig made their way into the courthouse, the two men led their supporters in chants of “Love Wins.”

After the arguments, Phillips told reporters that the backlash against his business after his refusal has included death threats and harassment, adding, “We are struggling just to make ends meet and keep the shop afloat.”

“It’s hard to believe that the government is forcing me choose between providing for my family and my employees, and violating my relationship with God,” Phillips said.

Mullins told reporters the couple’s snub by Phillips made them feel mortified and humiliated, like “second-class citizens in our society.”

The Colorado Civil Rights Commission found that Phillips had violated anti-discrimination law and ordered him to take remedial measures including staff training and the filing of quarterly compliance reports. The baker lost appeals in state courts before asking the U.S. Supreme Court to hear the case.

(Reporting by Lawrence Hurley; Additional reporting by Andrew Chung; Editing by Will Dunham)